Thyroid nodules with FNA cytology suspicious for follicular variant of papillary thyroid carcinoma: follow-up and management

Abstract

Thyroid nodules diagnosed as follicular neoplasm on fine-needle aspiration biopsy (FNAB) may represent hyperplastic/adenomatous nodules, follicular adenoma or carcinoma, and follicular variants of papillary thyroid carcinoma (FVPTC) on histologic follow-up. In our laboratory, we attempted to identify a subset of cases which showed cellular specimens with focal features (nuclear chromatin clearing, membrane thickening, and rare grooves) suspicious for the follicular variant of papillary thyroid carcinoma. These cases are reported as follicular-derived neoplasms with nuclear features suspicious for FVPTC to distinguish them from those diagnosed as follicular neoplasm. This study documents our experience with 52 cases so diagnosed and followed prospectively with histologic follow-up. A neoplastic nodule was confirmed in 45/52 cases (86%), of which 40 were malignant (77%). FVPTC was identified in 35/52 cases (67%). Four cases were usual papillary carcinoma, 3 were follicular adenoma, 2 were Hürthle-cell adenoma, and 1 was insular carcinoma. In 7 cases, the subsequent histologic findings were nonneoplastic (5 hyperplastic nodules and 2 colloid nodules). Our prospective study shows that in cellular smears from thyroid nodules, a careful search for the nuclear features of papillary carcinoma should be performed, and it is appropriate to diagnose cases as suspicious for FVPTC if the nuclear features of papillary carcinoma are focal. The surgical management of this group may include an intraoperative confirmation of cytologic diagnosis by scrape preparation and/or frozen section in order to avoid a second surgical intervention for completion thyroidectomy.